1wk old chicks fussing at their bottoms

[cburnstein]

We got a mix of 21 chicks last week and all are doing well except for 2 of the Barred Rock chicks. They are frequently seen trying to reach their bottoms and one has actually worn the feathers off on her backside. They seem to be eating, drinking and pooping ok and their bellies are soft. Just not sure if I should be worried or not. This has been going on since we got them last Thursday. Any help is appreciated.